800MN forging press uses plate laminated parallel structure as the main bearing mode, where the force transfer and the stiffness match play key roles in achieving satisfactory performance of the equipment. Although the traditional design methods can obtain desirable stiffness or strength for bearing structure, they less consider the effect of manufacturing errors on the system performance and thus are ineffective. This is because manufacturing errors can cause local structure variation and heavy stress concentration, which may do great harms to the working performance of the equipment. In this paper, a new design approach is proposed to consider the effect of manufacturing errors to the system performance. First, a three-dimension finite element model of the 800MN forging press is built using Marc, upon which stress distributions and concentrations under different combination modes of manufacturing errors are studied. Then, combination law of manufacturing errors is established and validation is carried out through physic test.